Carbon nanotube (CNT for short) has been widely concerned and studied by academia and industry since it was discovered in Jan. 1991 by the Japanese physicist, Sumio Iijima, from carbon fibers produced by arc method using a high-resolution transmission electron microscopy. CNT is a tubular carbon molecule. Each carbon atom on the tube is SP2 hybridized, and carbon atoms are bonded to each other by a carbon-carbon σ bond, forming a honeycomb structure composed of hexagons as the CNT skeleton. The molecular structure of CNT decides its unique properties including excellent electrical properties, good thermal conductivity, high mechanical strength, and the like.
At present, CNT is widely applied in the fields such as display, sensors, RF circuits, flexible circuits, and so on. When applied to a thin film transistor (TFT), CNT is used as a material for the semiconductor layer. In the prior art, CNT is fabricated mainly by liquid phase method and gas phase method as the semiconductor layer in a TFT.
The liquid phase method is to disperse the prepared CNT in water or an organic solvent after purification, and fabricate it on a required substrate by immersion, spin coating, spraying, etc, thereby forming a semiconductor layer by patterning process. However, the CNTs in the semiconductor layer formed on the substrate by liquid phase method are generally a random network, and there are many CNT tube-tube junction contact nodes, resulting in a mobility of typically not more than 100 cm2/V.s. As a result, the potential of CNT is not exerted, and the uniformity and the channel positioning of the CNT network are poor.
In the gas phase method, CNT parallel arrays can be directly fabricated on a substrate, which can greatly reduce the number of CNT tube-tube junction contact nodes and increase the mobility. However, when the semiconductor layer is prepared by gas phase method, the temperature required is relatively high, the substrate for growing the CNT parallel arrays is very restricted, the proportion of metallic CNTs is difficult to decrease, and the device's switching performance is relatively poor.